Drinking three and a half glasses of wine a week is enough to raise the risk of dementia, researchers have warned.
Their study of more than 13,000 adults is the largest of its kind to show how even low levels of alcohol can harm the brain.
Men and women who drank a little over one unit of alcohol a day suffered a noticeable decline in their brains’ ability to function over four years.
One unit of alcohol is equivalent to around half a 175ml glass of wine, half a pint of beer or a measure of spirits.
Researchers from Oxford and Cardiff universities say adults who drink more than this amount are putting themselves at ‘significant risk’ of dementia.
They are also calling for a ‘discussion’ over whether the Government’s recommended alcohol limit of 14 units a week for both men and women should be lowered for older adults.
On Wednesday of next week, the Royal College of Psychiatrists will publish a review into the harm that drinking does to the over-60s.
Its authors believe that 14 units a week is an ‘unsafe’ level for many older adults because of the risk of dementia and other illnesses.
Dementia is now the leading cause of death in the UK. There are 61,000 new cases a year, and no sign of a cure.
Researchers say alcohol is contributing to these rising rates because it is toxic for the brain and damages the memory.
Professor Simon Moore, of Cardiff University, one of the lead authors, said: ‘We’re drinking ourselves to stupidity. If you want to remain healthy in your later years you should really minimise how much you drink.
‘If you’re planning on drinking more than ten grams a day (1.25 units) you’re increasing your risk of dementia. If, for example, last week you were drinking on average ten grams of alcohol a day, about a bottle of prosecco that week, but then next week you increase that to two bottles of prosecco, you’re putting yourself at significant risk.’
The study, published in the Journal of Public Health, looked at 13,342 adults aged 40 to 73. They took computer tests four and a half years apart that measured their brains’ ability to function. These tests are useful in predicting whether someone will develop dementia in later life.
Men and women who drank more than ten grams of alcohol a day performed much worse in the tests four and a half years on compared with those who drank less often.
This was even more pronounced amongst those adults over 60, suggesting their brains are more sensitive to alcohol.
Professor Moore said there were two probable ways in which low-level drinking harms the brain.
Firstly, it is thought to dissolve the nerve cells that send signals to the brain. As we get older, the brain loses its ability to generate new nerve cells so this damage is irreparable.
Secondly, doctors believe alcohol prevents the brain from absorbing the vitamin B1, which is crucial for the brain’s ability to work.
Last week, a study, published in the Lancet Public Health journal, showed that heavy drinking can treble the risk of developing dementia.
Researchers from the Translational Health Economics Network in Paris found that 39 % of those diagnosed with dementia before the age of 65 had signs of brain damage linked to alcohol.
But researchers say there is growing evidence that moderate amounts of alcohol are contributing to the illness.
Last summer, an Oxford University study – published in the British Medical Journal – found that adults who drank between 14 and 21 units of alcohol a week were much more likely to suffer damage to a part of their brain linked to dementia. It involved 550 men and women who had MRI scans on their brains.